Optimization of Enzymatic Gas-Phase Reactions by Increasing the Long-Term Stability of the Catalyst

Enzymatic gas-phase reactions are usually performed in continuous reactors, and thus very stable and active catalysts are required to perform such transformations on cost-effective levels. The present work is concerned with the reduction of gaseous acetophenone to enantiomerically pure (R)-1-phenylethanol catalyzed by solid alcohol dehydrogenase from Lactobacillus brevis (LBADH), immobilized onto glass beads. Initially, the catalyst preparation displayed a half-life of 1 day under reaction conditions at 40 °C and at a water activity of 0.5. It was shown that the observed decrease in activity is due to a degradation of the enzyme itself (LBADH) and not of the co-immobilized cofactor NADP. By the addition of sucrose to the cell extract before immobilization of the enzyme, the half-life of the catalyst preparation (at 40 °C) was increased 40 times. The stabilized catalyst preparation was employed in a continuous gas-phase reactor at different temperatures (25-60 °C). At 50 °C, a space-time yield of 107 g/L/d was achieved within the first 80 h of continuous reaction.

Scale-up from microtiter plate to laboratory fermenter: evaluation by online monitoring techniques of growth and protein expression in Escherichia coli and Hansenula polymorpha fermentations

<p>Abstract</p> <p>Background</p> <p>In the past decade, an enormous number of new bioprocesses have evolved in the biotechnology industry. These bioprocesses have to be developed fast and at a maximum productivity. Up to now, only few microbioreactors were developed to fulfill these demands and to facilitate sample processing. One predominant reaction platform is the shaken microtiter plate (MTP), which provides high-throughput at minimal expenses in time, money and work effort. By taking advantage of this simple and efficient microbioreactor array, a new online monitoring technique for biomass and fluorescence, called BioLector, has been recently developed. The combination of high-throughput and high information content makes the BioLector a very powerful tool in bioprocess development. Nevertheless, the scalabilty of results from the micro-scale to laboratory or even larger scales is very important for short development times. Therefore, engineering parameters regarding the reactor design and its operation conditions play an important role even on a micro-scale. In order to evaluate the scale-up from a microtiter plate scale (200 μL) to a stirred tank fermenter scale (1.4 L), two standard microbial expression systems, <it>Escherichia coli </it>and <it>Hansenula polymorpha</it>, were fermented in parallel at both scales and compared with regard to the biomass and protein formation.</p> <p>Results</p> <p>Volumetric mass transfer coefficients (k_La) ranging from 100 to 350 1/h were obtained in 96-well microtiter plates. Even with a suboptimal mass transfer condition in the microtiter plate compared to the stirred tank fermenter (k_La = 370-600 1/h), identical growth and protein expression kinetics were attained in bacteria and yeast fermentations. The bioprocess kinetics were evaluated by optical online measurements of biomass and protein concentrations exhibiting the same fermentation times and maximum signal deviations below 10% between the scales. In the experiments, the widely applied green fluorescent protein (<it>GFP</it>) served as an online reporter of protein expression for both strains.</p> <p>Conclusions</p> <p>The successful 7000-fold scale-up from a shaken microtiter plate to a stirred tank fermenter was demonstrated in parallel fermentations for standard microbial expression systems. This confirms that the very economical and time efficient platform of microtiter plates can be very easily scaled up to larger stirred tank fermenters under defined engineering conditions. New online monitoring techniques for microtiter plates, such as the BioLector, provide even more real-time kinetic data from fermentations than ever before and at an affordable price. This paves the way for a better understanding of the bioprocess and a more rational process design.</p

Использование потенциометрического метода для определения микроконцентраций фторид ионов в технологических водах АЭС

Disposable cylindrical shaken bioreactors using plastic bags or vessels represent a promising alternative to stainless steel bioreactors, because they are flexible, cost-effective and can be pre-sterilized. Unlike conventional well-established steel bioreactors, however, such disposable bioreactor systems have not yet been precisely characterized. Thus, the aim of this current work is to introduce a new power input correlation as a potential means to characterize the hydrodynamics of these new systems. A set of rel- evant power input variables was defined and transformed into dimensionless numbers by using the Buckingham’s pi-Theorem. These numbers were then experimentally varied to quantify the relationship among the numbers. A simple correlation was generated for the power input with seven variables. The application of this new correlation was validated using 200 L and 2000 L orbitally shaken bioreactors. In conclusion, the proposed correlation is a useful tool to predict the power input and hydrodynamics during cell cultivation in cylindrical shaken bioreactors of all scales

University transcultural space: everyday cultural practice of foreign students

Показано, что площадкой для отслеживания динамики траскультурных процессов является образовательная среда. Академическая мобильность позволяет интегрировать собственные культурные атрибуты человека в новую среду, распространяя тенденции транскультурности. Мобильность трансформирует мировосприятие, пространственно-временные и культурные границы. Сделан вывод о том, что транскультурная среда стимулирует к осознанию ситуации наличия "своей" и "чужой" культуры, необходимости выбирать оптимальные пути взаимодействия с "Другим", сравнительному анализу культур через повседневные культурные практики, толерантному отношению к представителям других культур и самовосприятию в ином культурном контексте

Удосконалення транспортно-технологічної схеми доставки будівельних матеріалів до основних споживачів м. Одеса

Важливим процесом у підвищенні ефективності перевізного процесу є маршрутизація перевезень. Від її правильної побудови залежить рівень переваг серед конкурентів. Найбільш вагомою перевагою виступає формування та використання раціональних маршрутів при перевезенні вантажів. Розробка раціональних транспортно-технологічних схем дозволяє підвищити продуктивність вантажних автомобілей, зменшити їх кількість та прискорити час доставки вантажів, й відповідно, підвищити якість перевізного процесу. Удосконалення транспортно-технологічних схем доставки будівельних матеріалів поліпшить умови обслуговування клієнтури, дозволить своєчасно реагувати на зміну обсягу транспортних послуг, що в свою чергу позначиться на економічних показниках господарської діяльності різних сфер. Завдання ускладняється й ще тому, що доставка вантажів виконується у межах мегаполісу з інтенсивним рухом громадського та власно

The inverse stationary heat conduction problem for a cuboid

The heat conductivity coefficient is important characteristic which is used in various spheres. The original methodic for conductivity coefficient determination was proposed for samples in form of rectangular parallelepiped. The results of numerical solution of nonlinear heat conduction problem in heat conduction coefficient value range 0.04-5 W/(m K) with different sample relative size were presented

Optimized polymer-based glucose release in microtiter plates for small-scale E. coli fed-batch cultivations

Background: Small-scale cultivation vessels, which allow fed-batch operation mode, become more and more important for fast and reliable early process development. Recently, the polymer-based feeding system was introduced to allow fed-batch conditions in microtiter plates. Maximum glucose release rates of 0.35 mg/h per well (48-well-plate) at 37 °C can be achieved with these plates, depending on the media properties. The fed-batch cultivation of fluorescent protein-expressing E. coli at oxygen transfer rate levels of 5 mmol/L/h proved to be superior compared to simple batch cultivations. However, literature suggests that higher glucose release rates than achieved with the currently available fed-batch microtiter plate are beneficial, especially for fast-growing microorganisms. During the fed-batch phase of the cultivation, a resulting oxygen transfer rate level of 28 mmol/L/h should be achieved. Results: Customization of the polymer matrix enabled a considerable increase in the glucose release rate of more than 250% to up to 0.90 mg/h per well. Therefore, the molecular weight of the prepolymer and the addition of a hydrophilic PDMS-PEG copolymer allowed for the individual adjustment of a targeted glucose release rate. The newly developed polymer matrix was additionally invariant to medium properties like the osmotic concentration or the pH-value. The glucose release rate of the optimized matrix was constant in various synthetic and complex media. Fed-batch cultivations of E. coli in microtiter plates with the optimized matrix revealed elevated oxygen transfer rates during the fed-batch phase of approximately 28 mmol/L/h. However, these increased glucose release rates resulted in a prolonged initial batch phase and oxygen limitations. The newly developed polymer-based feeding system provides options to manufacture individual feed rates in a range from 0.24-0.90 mg/h per well. Conclusions: The optimized polymer-based fed-batch microtiter plate allows higher reproducibility of fed-batch experiments since cultivation media properties have almost no influence on the release rate. The adjustment of individual feeding rates in a wide range supports the early process development for slow, average and fast-growing microorganisms in microtiter plates. The study underlines the importance of a detailed understanding of the metabolic behavior (through online monitoring techniques) to identify optimal feed rates. © 2020 The Author(s)

Potential errors in conventional DOT measurement techniques in shake flasks and verification using a rotating flexitube optical sensor

<p>Abstract</p> <p>Background</p> <p>Dissolved oxygen tension (DOT) is an important parameter for evaluating a bioprocess. Conventional means to measure DOT in shake flasks using fixed Clark-type electrodes immersed in the bulk liquid are problematic, because they inherently alter the hydrodynamics of the systems. Other approaches to measure DOT that apply fluorescing sensor spots fixed at the inside wall of a shake flask are also suboptimal. At low filling volumes for cultivating microorganisms with a high oxygen demand, the measured DOT signal may be erroneous. Here, the sensor spot is sometimes exposed to gas in the head space of the flask. Merely repositioning the sensor spot elsewhere in the flask does not address this problem, since there is no location in the shake flask that is always covered by the rotating bulk liquid. Thus, the aim of this prospective study is first, to verify the systemic error of Clark-type electrodes for measuring DOT in shake flasks. The second principle aim is to use the newly built "flexitube optical sensor" to verify potential errors in conventional optical DOT measurements based on fixed sensor spots.</p> <p>Results</p> <p>With the Clark-type electrode, the maximum oxygen transfer capacity in shake flasks rose compared to that of an analogous system without an electrode. This proves changed hydrodynamics in the system with the Clark-type electrode. Furthermore, regarding the sensor spot experiments under oxygen-limited conditions where the DOT value ought to approach zero, the acquired signals were clearly above zero. This implies that the sensor spot is influenced by oxygen present in the headspace and not only by oxygen in the bulk liquid.</p> <p>Conclusions</p> <p>The Clark-type electrode is unsuitable for measuring DOT. Moreover, the newly built rotating flexitube optical sensor is useful to verify potential errors of conventional optical DOT measurement techniques applying fixed sensor spots.</p